Factors affecting nectar sugar composition in chiropterophilic plants

AbstractMost pollinators prefer the sugars present in the nectar they consume, so it has been hypothesized that they have molded nectar trait evolution. However, nectar-feeding bats do not exhibit preferences for the sugars present in their diet. We analyzed the role that biochemical and ecological factors could play in shaping the nectar traits of chiropterophilic plants. We studied nectar traits and flower production in 49 plant species. We evaluated the relationship between nectar concentration and sugar composition using phylogenetically independent contrasts and if nectar traits were related to flower production using a Manova. We found that 42 species produced high hexoses nectars, and 7 species produced sucrose rich nectars. Phylogenetically independent contrasts showed that nectar concentration was negatively related to glucose content, positively related to fructose content, and was not related to sucrose content. A negative relationship was found from glucose and fructose contents to sucrose content, and glucose content was negatively related to fructose content. Finally, we did not found any relationship between nectar traits and the plants’ flowering strategies. We conclude that bat physiology and the relative low evolutionary time of the interaction between plants and bats may determine the lack of pattern in the nectar characteristics of chiropterophilic plants

Extended WKB method, resonances and supersymmetric radial barriers

Semiclassical approximations are implemented in the calculation of position and width of low energy resonances for radial barriers. The numerical integrations are delimited by t/T<<8, with t the period of a classical particle in the barrier trap and T the resonance lifetime. These energies are used in the construction of `haired' short range potentials as the supersymmetric partners of a given radial barrier. The new potentials could be useful in the study of the transient phenomena which give rise to the Moshinsky's diffraction in time.Comment: 12 pages, 4 figures, 3 table

Entamoeba histolytica Up-Regulates MicroRNA-643 to Promote Apoptosis by Targeting XIAP in Human Epithelial Colon Cells

MicroRNAs (miRNAs) are small non-coding RNAs that function as negative regulators of gene expression. Recent evidences suggested that host cells miRNAs are involved in the progression of infectious diseases, but its role in amoebiasis remains largely unknown. Here, we reported an unexplored role for miRNAs of human epithelial colon cells during the apoptosis induced by Entamoeba histolytica. We demonstrated for the first time that SW-480 colon cells change their miRNAs profile in response to parasite exposure. Our data showed that virulent E. histolytica trophozoites induced apoptosis of SW-480 colon cells after 45 min interaction, which was associated to caspases-3 and -9 activation. Comprehensive profiling of 667 miRNAs using Taqman Low-Density Arrays showed that 6 and 15 miRNAs were significantly (FC &gt; 1.5; p &lt; 0.05) modulated in SW-480 cells after 45 and 75 min interaction with parasites, respectively. Remarkably, no significant regulation of the 6-miRNAs signature (miR-526b-5p, miR-150, miR-643, miR-615-5p, miR-525, and miR-409-3p) was found when SW-480 cells were exposed to non-virulent Entamoeba dispar. Moreover, we confirmed that miR-150, miR-643, miR-615-5p, and miR-525 exhibited similar regulation in SW-480 and Caco2 colon cells after 45 min interaction with trophozoites. Exhaustive bioinformatic analysis of the six-miRNAs signature revealed intricate miRNAs-mRNAs co-regulation networks in which the anti-apoptotic XIAP, API5, BCL2, and AKT1 genes were the major targets of the set of six-miRNAs. Of these, we focused in the study of functional relationships between miR-643, upregulated at 45 min interaction, and its predicted target X-linked inhibitor of apoptosis protein (XIAP). Interestingly, interplay of amoeba with SW-480 cells resulted in downregulation of XIAP consistent with apoptosis activation. More importantly, loss of function studies using antagomiRs showed that forced inhibition of miR-643 leads to restoration of XIAP levels and suppression of both apoptosis and caspases-3 and -9 activation. Congruently, mechanistic studies using luciferase reporter assays confirmed that miR-643 exerts a postranscripcional negative regulation of XIAP by targeting its 3′-UTR indicating that it's a downstream effector. In summary, we provide novel lines of evidence suggesting that early-branched eukaryote E. histolytica may promote apoptosis of human colon cells by modulating, in part, the host microRNome which highlight an unexpected role for miRNA-643/XIAP axis in the host cellular response to parasites infection

Phylogenetic classification of the world's tropical forests

Knowledge about the biogeographic affinities of the world’s tropical forests helps to better understand regional differences in forest structure, diversity, composition, and dynamics. Such understanding will enable anticipation of region-specific responses to global environmental change. Modern phylogenies, in combination with broad coverage of species inventory data, now allow for global biogeographic analyses that take species evolutionary distance into account. Here we present a classification of the world’s tropical forests based on their phylogenetic similarity. We identify five principal floristic regions and their floristic relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. Our results do not support the traditional neo- versus paleotropical forest division but instead separate the combined American and African forests from their Indo-Pacific counterparts. We also find indications for the existence of a global dry forest region, with representatives in America, Africa, Madagascar, and India. Additionally, a northern-hemisphere Subtropical forest region was identified with representatives in Asia and America, providing support for a link between Asian and American northern-hemisphere forests.</p

Partial and asymmetrical reproductive isolation between two sympatric tropical shrub species: Cnidoscolus aconitifolius and C. souzae (Euphorbiaceae)

Abstract Reproductive isolation is conferred by several barriers that occur at different stages of reproduction. Comprehensive reviews on the topic have identified that barriers occurring prior to zygote formation are often stronger than those that occur afterward. However, the overrepresentation of temperate perennial herbs in the current literature precludes any generalization of this pattern to plants that present other life forms and patterns of distribution. Here, we assessed reproductive isolation barriers and their absolute contribution to reproductive isolation and asymmetry in Cnidoscolus aconitifolius and C. souzae, two closely related tropical shrub species that co‐occur on the Yucatan peninsula. The reproductive barriers assessed were phenological mismatch, pollinator differentiation, pollen–pistil incompatibility (three pre‐zygotic barriers), fruit set failure, and seed unviability (post‐zygotic barriers). Reproductive isolation between the study species was found to be complete in the direction C. aconitifolius to C. souzae, but only partial in the opposite direction. One post‐zygotic barrier was the strongest example. Most barriers, particularly the pre‐zygotic examples, were asymmetrical and predicted the direction of heterospecific pollen flow and hybrid formation from C. souzae to C. aconitifolius. Both parental species, as well as the hybrids, were diploid and had a chromosome number 2n = 36. More studies with tropical woody perennials are required to fully determine whether this group of plants consistently shows stronger post‐zygotic barriers

High Prevalence Anti-Trypanosoma cruzi Antibodies, among Blood Donors in the State of Puebla, a Non-endemic Area of Mexico

Blood transfusion is the second most common transmission route of Chagas disease in many Latin American countries. In Mexico, the prevalence of Chagas disease and impact of transfusion of Trypanosoma cruzi -contaminated blood is not clear. We determined the seropositivity to T. cruzi in a representative random sample, of 2,140 blood donors (1,423 men and 647 women, aged 19-65 years), from a non-endemic state of almost 5 millions of inhabitants by the indirect hemagglutination (IHA) and enzyme linked immunosorbent assay (ELISA) tests using one autochthonous antigen from T. cruzi parasites, which were genetically characterized like TBAR/ME/1997/RyC-V1 (T. cruzi I) isolated from a Triatoma barberi specimen collected in the same locality. The seropositivity was up to 8.5% and 9% with IHA and ELISA tests, respectively, and up to 7.7% using both tests in common. We found high seroprevalence in a non-endemic area of Mexico, comparable to endemic countries where the disease occurs, e.g. Brazil (0.7%), Bolivia (13.7%) and Argentina (3.5%). The highest values observed in samples from urban areas, associated to continuous rural emigration and the absence of control in blood donors, suggest unsuspected high risk of transmission of T. cruzi, higher than those reported for infections by blood e.g. hepatitis (0.1%) and AIDS (0.1%) in the same region